This present invention relates to manufacture of electrochemical cells. More particularly, the present invention provides a method and system for providing a design and using such design for manufacture of three-dimensional elements for three-dimensional electrochemical cells. Merely by way of example, the invention has been provided with use of lithium based cells, but it would be recognized that other materials such as zinc, silver, copper and nickel could be designed in the same or like fashion. Additionally, such batteries can be used for a variety of applications such as portable electronics (cell phones, personal digital assistants, music players, video cameras, and the like), power tools, power supplies for military use (communications, lighting, imaging and the like), power supplies for aerospace applications (power for satellites), and power supplies for vehicle applications (hybrid electric vehicles, plug-in hybrid electric vehicles, and fully electric vehicles). The design of such batteries is also applicable to cases in which the battery is not the only power supply in the system, and additional power is provided by a fuel cell, other battery, IC engine or other combustion device, capacitor, solar cell, etc.
A typical conventional electrochemical cell, commonly known as a battery, consists of a positive electrode, negative electrode, a separator, an electrolyte, a container, and tabs extending from the electrode and extending through the exterior of the container. Electrochemical cells and batteries are classified as primary (non-rechargeable), and secondary (rechargeable). Upon discharge, anode atoms lose electrons to the external circuitry and they oxidize to ions; at the same time ions at the cathode gain electrons and ions from the external circuitry and electrolyte, respectively. Upon charge, the reverse occurs: ions at anode regain electrons and reduce back to atoms, while atoms at cathode lose electrons and ions to the external circuitry and electrolyte, respectively. During these processes, ions are transported through the electrolyte. Design and manufacturing of facile, accessible pathways for both electron and ions are important factors in achieving high rate performance and high specific and gravimetric energy in electrochemical cells.
Conventional batteries generally have one of three form factors: cylindrical, prismatic, and button cells. The form factors influence electrode design. The form factors also affect cell performance characteristics, including capacity and rate capability, because they increase internal electrical resistance and resistance to heat dissipation. Electrodes are commonly manufactured as one of three basic types, wherein 1) cathode and anode comprise concentric cylinders (cylindrical configuration), 2) cathode, anode and separator are spirally wound in a “jelly roll” configuration (also a cylindrical configuration), or 3) cathode and anode are manufactured in a flat-plate configuration (prismatic configuration). The concentric cylinders design generally has higher energy and capacity, because it generally maximizes the amount of active material packed inside the cell. However, the jelly roll and flat plate design frequently offer higher rate performance, because of higher surface areas. In general, high aspect-ratio (length-to-diameter ratio) cylindrical cells generally offer lower internal resistance and better rate capabilities than lower aspect-ratio cylindrical cells. Higher discharge rate capability is generally a result of higher surface area-to-volume ratios.
Conventional manufacturing processes for electrodes involve multiple manufacturing processes. That is, conventional manufacturing of electrodes include casting a paste of mixtures of active materials, conductive additives, binder, and solvent onto a metal substrate to form an electrode. Next, the paste of mixtures making up the electrode is dried in a high temperature oven or at room temperature. The electrode is laminated to a sufficiently low thickness to assure good contact among the constituent particles. Performance targets for electrochemical cells include adequate specific energy/power and energy/power density, cell and module robustness, safety, aging characteristics, lifetime, thermal behavior, and material/shelf life.
Unfortunately, limitations exist in designing and manufacturing the electrochemical cells. Achieving the performance targets is accomplished through trial and error, which is tedious and time consuming. Often times, cell capacity and chemistry are selected. The quantity of material for the chemistry is selected for the electrode. The material is provided in one of the three configurations. The resulting battery is tested to determine whether the performance targets have been met, which is generally not the case even after repeated trial and error. Single dimensional simulation within the battery is performed. The amount of active materials used in the electrodes is calculated and recalculated based on targeted capacity. Other parameters including electrode thicknesses, electrolyte compositions, and types and concentrations of additives are typically adjusted until cycle-life and safety targets are met. Clearly, a time-consuming, inefficient, and tedious, process!
Several published literature reports attempt to provide systematic and numerical approaches to analyzing conventional batteries. These reports pertain to the amount of active materials, conductive additives, binder and porosity of the electrode, and the degree of compression. A pioneering approached was described in “C.-W. Wang, and A. M. Sastry, Mesoscale Modeling of a Li-Ion Polymer Cell, Journal of the Electrochemical Society,” 154 [11] A1035-A1047 (2007), and Y.-H. Chen, C.-W. Wang, G. Liu, X.-Y. Song, V. S. Battaglia, and A. M. Sastry, Selection of Conductive Additives in Li-ion Battery Cathodes: “A Numerical Study, Journal of the Electrochemical Society, 154 [10] A978-A986 (2007).” Although highly successful, such approaches were limited.
Therefore, it is highly desirable to find ways of improving and designing electrochemical cells, which holistically accounts for key manufacturing and performance parameters.